> On Di, 12.05.20 14:21, Fedora Development ML
> (devel(a)lists.fedoraproject.org) wrote:
>
> ...
>
> cgroupsv2 is built around a single-writer scheme. That means any
> section of the tree shall only have a singler writer, i.e. one
> subsystem 'owning' it. On systemd systems the root of the tree is
> owned by systemd, it's the single writer of it. Other software may
> read from the tree but not make changes to it.
>
> You can ask systemd for a delegated subtree of the main cgroup tree
> however. You can do this via Delegate=yes in a service file, or by
> doing "systemd-run --scope -p Delegate=yes -t /bin/bash" on the
> command line. If you do that you get your own subtree in which you can
> do whatever you want, and systemd will not step on your toes.
>
> Making changes to the top-level cgroup tree, i.e. stepping into
> systemd's explicitly owned territory means voiding your warranty
> though.
>
> This design choice is made by the cgroupsv2 subsystem in the kernel
> btw, it's not something systemd came up with.
>
> It's documented here in all detail:
> https://systemd.io/CGROUP_DELEGATION
>
> hence, if libcgroups wants to do cgroup stuff it really needs to ask
> systemd for delegation first (or be invoked inside a service where
> something else asked for it). If it doesn't then it's simply broken.
Thank you for the explanation. The page you linked is more than clear upfront:
Intended audience: hackers working on userspace subsystems that require
direct cgroup access, such as container managers and similar.
I will keep that in mind.
>
> In general, I am not sure why one would even want the cgroup tools on
> a systemd system though.
I just wrote something along those lines to Tom, the onus is on me to catch-up
and leverage what is available.
> We should provide most of it natively anyway,
> though possibly in a different manner.
>
> Lennart
>
> --
> Lennart Poettering, Berlin
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